Submerged arc furnace process superior to the Waelz process in reducing PCDD/F emission during thermal treatment of electric arc furnace dust

Besides the Waelz process, the submerged arc furnace (SAF) process has also been extensively used to retain metals from ashes and scraps in the metallurgical industry. However, very little is known about the formation and depletion of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from this thermal process. In this study, an electric arc furnace (EAF) dust treatment plant adopting the SAP process was investigated and compared to the plant adopting the Waelz process. The predominant contributor of PCDD/F I-TEQ input was the EAF dusts, accounting for 98.4% of the total. The PCDD/F contents in the generated fly ashes of the SAP were extremely low, as almost all the organic compounds for PCDD/F formation were decomposed by the high operating temperatures (1500-1700 degrees C) of the SAF Therefore, the PCDD/F emission factor of the SAP process (46.9 mu g I-TEQ/tonne-EAF dust) was significantly lower than that of the Waelz process (840-1120 mu g I-TEQ/ tonne-EAF dust). Its PCDD/F output/input ratios (0.23 and 0.50 based on mass and toxicity) were also lower than those of the Waelz process plant (0.62 and 1.19). Therefore, the SAF,process is superior to the Waelz process in reducing the potential of PCDD/F formation. (C) 2013 Elsevier B.V. All rights reserved.